Experimental study on flow boiling heat transfer of a new azeotropic mixture of R1234ze(E)/R600a in a horizontal tube

Recently, considerable attention has been given to new environment-friendly refrigerant mixtures for applications such as heat pumps and air conditioners. This study presents flow boiling heat transfer characteristics of environment-friendly refrigerant mixture of R1234ze(E)/R600a (0.148/0.852, 0.194/0.806, 0.371/0.629, 0.623/0.377 and 0.797/0.203 by mole fraction) in a smooth horizontal tube with an inner diameter of 6 mm. The experiments were conducted at saturation pressures from 0.215 to 0.415 MPa, mass fluxes from 67 to 194 kg m−2 s−1 and heat fluxes from 10.6 to 74.8 kW m−2. The influences of concentration, saturation pressure, mass flux and heat flux on heat transfer were analyzed and discussed. Furthermore, the experimental data were also compared with nine well-known flow boiling heat transfer correlations. The results indicated that correlation of Liu and Winterton (1991), which is the correlation for pure fluids, gives the best fit to the experimental data with a mean relative deviation of 18.2%. Finally, a new heat transfer correlation based on power-additive model was proposed and two suppression factors Smix and Fmix were introduced into the new correlation by taking account of mass transfer resistance. The new correlation makes great progress in the prediction accuracy with a mean relative deviation of 6.4%.